The disclosure generally relates to a power converter circuit of an illumination system and, more particularly, to the power converter circuit with better compatibility.
Due to the depletion of natural resources, people are paying more and more attention to energy conservation and environmental protection issues. Accordingly, illumination devices with less energy efficiency (e.g., incandescent lamps, or halogen lamps) are gradually replaced by illumination devices with higher energy efficiency. The light-emitting diode (LED) has advantages of high luminous efficiency, long life time, compact size, fast start time, high reliability, good durability, etc. Therefore, low power illumination devices such as the LEDs have become more and more popular and been adopted in home, office, street signs, street lights and other indoor and outdoor places for replacing traditional illumination devices.
Many low power illumination devices are manufactured in the form of standard bulbs or tubes to directly replace traditional bulbs or tubes. For example, LEDs may be made into T8 tubes, E27 bulbs, and MR16 lamps. It is, however, difficult to replace many circuit components of the illumination system already installed in the building (e.g., dimmers, electric transformers, and ballasts). If the traditional bulbs or tubes are directly replaced by the low power illumination devices, the low power illumination devices usually have problem when cooperating with traditional circuit components installed in the building. Therefore, the low power illumination device may not be lighted up or may flicker.
The electric transformer is so compact that it is usually utilized in the illumination system. The electric transformer comprises oscillating circuits and other circuit components for providing the required voltage signal with a higher oscillating frequency. The load of the electric transformer must draw enough current to enable the normal operation of the electric transformer. The energy consumption of the low power illumination devices, however, are usually far less than the energy consumption of the traditional lamps, and the low power illumination device may not draw enough current from the electric transformer. Consequently, the low power illumination device usually may not function normally when cooperating with traditional circuit components in the illumination system.
Besides, the phase-cut dimmer is usually adopted in many traditional illumination devices to adjust the brightness of the illumination device. The phase-cut dimmer usually adopts a diode or a triode for alternating current (TRIAC) to cut off a portion of an alternating current (AC) signal so as to adjust the brightness of the illumination device. When the AC signal is cut off, the voltage or the current of the AC signal is configured to be zero or a small value. The brightness of the low power illumination devices (e.g., LEDs), however, may not be adjusted properly when cooperating with the dimmer and the electric transformer. Thus, the low power illumination devices may flicker or may not be lighted up when cooperating with the dimmer and the electric transformer.
U.S. Patent Application No. 2012/0169246A1 discloses an illumination device and a driving method to solve the aforementioned compatibility problem by alternately operating the power converter circuit between a current generating mode and an off mode. Even if the technique of the aforementioned application is adopted, the compatibility problem still occurs when the low power illumination device cooperates with the dimmer and the electric transformer. Thus, the brightness of the low power illumination device still may not be adjusted properly.